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CentOS 7.0 - man page for zcgesv (centos section 3)

zcgesv.f(3)				      LAPACK				      zcgesv.f(3)

       zcgesv.f -

       subroutine zcgesv (N, NRHS, A, LDA, IPIV, B, LDB, X, LDX, WORK, SWORK, RWORK, ITER, INFO)
	    ZCGESV computes the solution to system of linear equations A * X = B for GE matrices
	   (mixed precision with iterative refinement)

Function/Subroutine Documentation
   subroutine zcgesv (integerN, integerNRHS, complex*16, dimension( lda, * )A, integerLDA,
       integer, dimension( * )IPIV, complex*16, dimension( ldb, * )B, integerLDB, complex*16,
       dimension( ldx, * )X, integerLDX, complex*16, dimension( n, * )WORK, complex, dimension( *
       )SWORK, double precision, dimension( * )RWORK, integerITER, integerINFO)
	ZCGESV computes the solution to system of linear equations A * X = B for GE matrices
       (mixed precision with iterative refinement)


	    ZCGESV computes the solution to a complex system of linear equations
	       A * X = B,
	    where A is an N-by-N matrix and X and B are N-by-NRHS matrices.

	    ZCGESV first attempts to factorize the matrix in COMPLEX and use this
	    factorization within an iterative refinement procedure to produce a
	    solution with COMPLEX*16 normwise backward error quality (see below).
	    If the approach fails the method switches to a COMPLEX*16
	    factorization and solve.

	    The iterative refinement is not going to be a winning strategy if
	    the ratio COMPLEX performance over COMPLEX*16 performance is too
	    small. A reasonable strategy should take the number of right-hand
	    sides and the size of the matrix into account. This might be done
	    with a call to ILAENV in the future. Up to now, we always try
	    iterative refinement.

	    The iterative refinement process is stopped if
	    or for all the RHS we have:
		o ITER is the number of the current iteration in the iterative
		  refinement process
		o RNRM is the infinity-norm of the residual
		o XNRM is the infinity-norm of the solution
		o ANRM is the infinity-operator-norm of the matrix A
		o EPS is the machine epsilon returned by DLAMCH('Epsilon')
	    The value ITERMAX and BWDMAX are fixed to 30 and 1.0D+00


		     N is INTEGER
		     The number of linear equations, i.e., the order of the
		     matrix A.	N >= 0.


		     NRHS is INTEGER
		     The number of right hand sides, i.e., the number of columns
		     of the matrix B.  NRHS >= 0.


		     A is COMPLEX*16 array,
		     dimension (LDA,N)
		     On entry, the N-by-N coefficient matrix A.
		     On exit, if iterative refinement has been successfully used
		     (INFO.EQ.0 and ITER.GE.0, see description below), then A is
		     unchanged, if double precision factorization has been used
		     (INFO.EQ.0 and ITER.LT.0, see description below), then the
		     array A contains the factors L and U from the factorization
		     A = P*L*U; the unit diagonal elements of L are not stored.


		     LDA is INTEGER
		     The leading dimension of the array A.  LDA >= max(1,N).


		     IPIV is INTEGER array, dimension (N)
		     The pivot indices that define the permutation matrix P;
		     row i of the matrix was interchanged with row IPIV(i).
		     Corresponds either to the single precision factorization
		     (if INFO.EQ.0 and ITER.GE.0) or the double precision
		     factorization (if INFO.EQ.0 and ITER.LT.0).


		     B is COMPLEX*16 array, dimension (LDB,NRHS)
		     The N-by-NRHS right hand side matrix B.


		     LDB is INTEGER
		     The leading dimension of the array B.  LDB >= max(1,N).


		     X is COMPLEX*16 array, dimension (LDX,NRHS)
		     If INFO = 0, the N-by-NRHS solution matrix X.


		     LDX is INTEGER
		     The leading dimension of the array X.  LDX >= max(1,N).


		     WORK is COMPLEX*16 array, dimension (N*NRHS)
		     This array is used to hold the residual vectors.


		     SWORK is COMPLEX array, dimension (N*(N+NRHS))
		     This array is used to use the single precision matrix and the
		     right-hand sides or solutions in single precision.


		     RWORK is DOUBLE PRECISION array, dimension (N)


		     ITER is INTEGER
		     < 0: iterative refinement has failed, COMPLEX*16
			  factorization has been performed
			  -1 : the routine fell back to full precision for
			       implementation- or machine-specific reasons
			  -2 : narrowing the precision induced an overflow,
			       the routine fell back to full precision
			  -3 : failure of CGETRF
			  -31: stop the iterative refinement after the 30th
		     > 0: iterative refinement has been sucessfully used.
			  Returns the number of iterations


		     INFO is INTEGER
		     = 0:  successful exit
		     < 0:  if INFO = -i, the i-th argument had an illegal value
		     > 0:  if INFO = i, U(i,i) computed in COMPLEX*16 is exactly
			   zero.  The factorization has been completed, but the
			   factor U is exactly singular, so the solution
			   could not be computed.

	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

	   November 2011

       Definition at line 201 of file zcgesv.f.

       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      zcgesv.f(3)

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